summaryrefslogtreecommitdiffstats
path: root/src/livarot/AlphaLigne.h
diff options
context:
space:
mode:
Diffstat (limited to '')
-rw-r--r--src/livarot/AlphaLigne.h87
1 files changed, 87 insertions, 0 deletions
diff --git a/src/livarot/AlphaLigne.h b/src/livarot/AlphaLigne.h
new file mode 100644
index 0000000..a192e1c
--- /dev/null
+++ b/src/livarot/AlphaLigne.h
@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/** @file
+ * TODO: insert short description here
+ *//*
+ * Authors:
+ * see git history
+ * Fred
+ *
+ * Copyright (C) 2018 Authors
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+#ifndef my_alpha_ligne
+#define my_alpha_ligne
+
+#include "LivarotDefs.h"
+
+/*
+ * pixel coverage of a line, libart style: each pixel coverage is obtained from the coverage of the previous one by
+ * adding a delta given by a step. the goal is to have only a limited number of positions where the delta != 0, so that
+ * you only have to store a limited number of steps.
+ */
+
+// a step
+struct alpha_step {
+ int x; // position
+ float delta; // increase or decrease in pixel coverage with respect to the coverage of the previous pixel
+};
+
+
+class AlphaLigne {
+public:
+ // bounds of the line
+ // necessary since the visible portion of the canvas is bounded, and you need to compute
+ // the value of the pixel "just before the visible portion of the line"
+ int min,max;
+ int length;
+
+ // before is the step containing the delta relative to a pixel infinitely far on the left of the line
+ // thus the initial pixel coverage is before.delta
+ alpha_step before,after;
+ // array of steps
+ int nbStep,maxStep;
+ alpha_step* steps;
+
+ // bounds of the portion of the line that has received some coverage
+ int curMin,curMax;
+
+ // iMin and iMax are the bounds of the visible portion of the line
+ AlphaLigne(int iMin,int iMax);
+ virtual ~AlphaLigne();
+
+ // empties the line
+ void Reset();
+
+ // add some coverage.
+ // pente is (eval-sval)/(epos-spos), because you can compute it once per edge, and thus spare the
+ // CPU some potentially costly divisions
+ int AddBord(float spos,float sval,float epos,float eval,float iPente);
+ // version where you don't have the pente parameter
+ int AddBord(float spos,float sval,float epos,float eval);
+
+ // sorts the steps in increasing order. needed before you raster the line
+ void Flatten();
+
+ // debug dump of the steps
+ void Affiche();
+
+ // private
+ void AddRun(int st,float pente);
+
+ // raster the line in the buffer given in "dest", with the rasterization primitive worker
+ // worker() is given the color parameter each time it is called. the type of the function is
+ // defined in LivarotDefs.h
+ void Raster(raster_info &dest,void* color,RasterInRunFunc worker);
+
+ // also private. that's the comparison function given to qsort()
+ static int CmpStep(const void * p1, const void * p2) {
+ alpha_step* d1=(alpha_step*)p1;
+ alpha_step* d2=(alpha_step*)p2;
+ return d1->x - d2->x ;
+ };
+};
+
+
+#endif
+